Heaters for paint spray guns



y 1957 A. J. KAISER 2,793,279

v HEATERS FOR PAINT SPRAY GUNS Filed Oct. 4, 1954 2 Sheets-Sheet l,.,--.........--.."Mun-.."

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HEATERS FOR PA-INT SPRAY GUNS Filed Oct. 4, 1954 2 Sheets-Sheet 2 IN VEN TOR.

E57 5 fi m/m J, 54/51? United States Patent HEATERS FOR PAINT SPRAY GUNSArthur J. Kaiser, Denver, Colo. Application October 4, 1954, Serial No.460,115 2 Claims. (Cl. 219-39) This invention relates to air-operatedspray guns for applying surface coating materials and more particularlyto means for supplying heated surface coatings to the spray gun. Surfacecoating material must have a relatively light viscosity for proper sprayapplication. This viscosity can be obtained by the use of thinners orsolvents, with a resulting thinning of the applied coating. Thepreferred method, however, is to heat the coating material prior tospraying to reduce the viscosity to the proper spraying consistency.

The principal object of the invention is to provide a highly efficient,portable, electric heater which can be applied to any conventional spraygun and which will act to rapidly heat the surface coating material toreduce it to the proper application consistency immediately before itenters the spray gun and to provide a heater which will avoid injuringthe materials or the colors thereof by overheating or burning.

Certain of the modern resin surface coatings are too viscous for spraygun application and have a tendency to settle or set with a resultingclogging of the conveying conduits, etc.

Another object of the invention is to provide efficient means forsupplying these heavy surface coating materials to a conventional spraygun at a proper spraying consistency and which will maintain a constant,uniform supply to the gun without clogging the gun or the supplyconduits.

A further object of the invention is to provide means for supplying aspray gun which can be used for conveying dry or powdered materials to aconventional spray gun and which will act to supply a solvent to thematerials and agitate the materials and the solvent under the influenceof heat to the proper spraying consistency immediately before itsentrance into the gun so as to prevent setting or settling in the gunand its supply conduits.

A still further object is to provide highly efiicient mixing and heatingmeans for a conventional spray gun which can be attached to andsupported on the gun in place of the usual paint canister usedtherewith.

Other objects and advantages reside in the detail construction of theinvention, which is designed for simplicity, economy, and efliciency.These will become more apparent from the following description.

In the following detailed description of the invention, reference is hadto the accompanying drawing which forms a part hereof. Like numeralsrefer to like parts in all views of the drawing and throughout thedescription.

In the drawing:

Fig. 1 illustrates one arrangement of the improved apparatus forsupplying heated surface coating materials to a conventional paint gun;

Fig. 2 is an enlarged, vertical, longitudinal section through a heatingdevice employed in the arrangement of Fig. 1, with the interiorstructure partially broken away for illustrative purposes;

Fig. 3 is a still further enlarged, cross-section through the heatingdevice, taken on the line 3-3, Fig. 1;

2 ,793,279 Patented May 21, 1957 2 'Fig. 4 is a similar, cross-section,taken on the line 44, Fig. 1;

Fig. 5 is a side view, partially broken away, of an alternatearrangement of the invention;

Fig. 6 is a horizontal section looking downwardly on the line 66, Fig.5; and

Fig. 7 is a reduced scale side view of a third arrangement of theimproved material supply apparatus for spray guns.

In all arrangements on the drawing, a conventional spray gun of any ofthe standard types is indicated by the numeral 10, with its actuatingtrigger at 11, its spray head at 12, and its air supply hose at 13. Thegun, per se, forms no part of the present invention which relates tomeans for supplying the material to be sprayed to the gun. The supplyingmeans can be connected with and attached to the gun in any desiredmanner. Usually, such guns are provided with a downwardly extending,tubular, threaded sleeve 14 to which either a paint supply hose or apaint-containing canister may be attached.

The arrangement of the invention shown in Fig. 1 employs a hollowcylindrical heater adapted to be connected to the sleeve 14 of the gunin any desired manner for heating the paint or other surface coatingmaterial being supplied to the gun 10. The heater comprises acylindrical barrel 15 closed at its top by means of a threaded cap 16and provided with a threaded coupling nipple 19 at its bottom. Avertical paint chamber 18 extends vertically from the nipple 19throughout the length of the barrel 15 and terminates at its upperextremity above the cap 16 in a threaded coupling 48 for receiving anipple 17 for attachment to the sleeve 14 of the gun 10. The paintchamber 18 is preferably formed from relatively thin metal of high heatconductivity, such as aluminum or copper, and is preferably corrugatedvertically within the barrel 15 so as to increase the area of the heattransfer surface thereof.

An electrical heating element 20 of the immersion type, such as acal-rod or the like, is convoluted about the paint chamber 18 to providea plurality of vertical heating portions about the chamber 18 betweenthe latter and the barrel wall. Electrical current is supplied to theheating element 20 in any desired manner, such as by means of a flexiblecord 21, through a control switch 22 and a temperature controlthermostat of any suitable type contained Within a thermostat housing 23which is secured on the side of the barrel 15.

The entire barrel 15, exteriorly of the chamber 18 and the heatingelement 20 is filled with a non-volatile heattransfer fluid 24. Thisfluid should be of a type having an exceedingly high boiling point andan exceedingly low freezing point so that it may remain permanentlysealed in the barrel 15. Such a fluid might be one of the ethyleneglycol compounds or a recently discovered fluid known as liquid heat atetracresylsilicate having a boiling temperature of approximately 817 F.and a freezing point below It can be seen that the heating element 20will rapidly heat the transfer fluid 24 to any desired temperature,depending upon the setting of the thermostat in the thermostat housing23, and that if a surface coating liquid be passed upwardly through thepaint chamber 18, it will become heated by contact with the heated wallsof the chamber and will flow to the paint spray gun at the properpredetermined temperature for eflicient hot spraymg.

For all ordinary uses where it is desired to reduce viscosity by heat,the above described construction will be suflicient. However, for useswhere it is desired to supply a heavy viscous material to the heater, aconstruction as shown in Fig. 1 may be employed comprising a centraltank 25, closed by means of a suitable airtight lid 26.

is provided. Air under pressure is supplied to the tank through an airsupply conduit 27 controlled by the usual control and pressureregulating valves, as is common in paint spray tanks.

This improved tank, however, is provided witha hopper bottom 28 whichdischarges into a screw conveyor cyl inder 29. A flexible conduit orhose 30 is connected by means of terminal couplings 49 between theconveyor cylinder 29 and the lower nipple 19 of the heater. A flexiblescrew conveyor 31, formed, from rubber, neoprene, or one of the flexibleresins about a flexible axis shaft 32, extends throughout the length ofthe hose 3% and extends upwardly through the paint chamber 18 in theheater. The axis shaft 32 ofthe conveyor 31 extends through the screwconveyor cylinder 29 to any desired speed reduction gear mechanism 33driven from a suitable. motor 34.

It can be seen that as the screw conveyor 31 rotates, it will tend toforce the material discharging from the tank through the hose andupwardly through the paint chamber 18 to prevent stoppage or clogginguntil the material can be heated to the proper viscosity-reducingtemperature for spraying.

In Fig. 5, a'second arrangement of the invention is illustrated for usewhere it is desired to apply the fluid reservoir directly to the spraygun. This arrangement employs a heater similar to that previouslydescribed with reference to Fig. 1 comprising a heating barrel 35 filledwith heat transfer fluid and containing a coiled electrical heatingelement 36 and provided with a central paint chamber 37, similar to thechamber 18 previously described. In this form, however, the barrel 35 issuspended from a container lid 38' frornwhicha threaded nipple 3-9projects upwardly for attachment to the attachment nipple 17 of thespray gun. The lid 38 carries an electrical control thermostat within athermostat housing 41 through which electrical current is supplied froma cord 42 to the heating element 36.

Any suitable spray gun paint canister may be threaded into the lid 38and filled with the fluid to be supplied to the gun 10. The paint orother surface coating material therein will be heated by heat exchangefrom the barrel 35 and will be drawn upwardly through the heated centralpaint chamber 37'of the heater where it willbecome still further heatedbefore flowing to the spray gun for application.

For use with viscous materials or relatively heavy materials havingatendency to settle, a canister such as illustrated at 43, in Fig. 5, maybev used. This canister is provided with an agitator 44 positionedadjacent its bottom and driven in any suitable manner, such as by meansof a conventional, compressed air motor 45 contained within a canisterbase 46 and supplied with. compressed air through asuitable supplyhose'47. It can be seen that the air pressure usually available forpaint.

spraying will act to actuate the motor 45 and constantly rotate theagitator 44 to keep the paint or other fluid within the canister 43 inproper fluid condition.

For the application of certain ofthe more recentfastsetting resinsurface-coating compounds which. are diflicult to apply with a spraygun, an arrangement such as illustrated in Fig. 7 maybe used; Thisarrangement positions a heater, exactly similar to the heater of Fig. 1upon a conventional spray gun and connects. the heater to the gun bymeans of a downwardly extending supply 3 elbow 52 which is used forsupplying the heated material to the gun. A heater 51 is controlled by asuitable thermostat 40 and is supplied with surface coatingmatcrialthrough a T-fitting from a flexible supply hose 53 which may contain aflexible screw conveyor 54 similar to the hose 30 and the conveyor 31previously described. The hose 53 leads to an elevated material reservoir (not shown) so that material will flow to the heater 51 and the gununder the influence of gravity assisted by the conveyor 54. Thisconstruction is more particularly intended for feeding dry or pasteplastic materials where pressure feeding is not practical, and is alsointended for use with materials where a thinner or solvent must beapplied to the dry or paste materials immediately prior to applicationso as to prevent setting of the material in the spray apparatus. Such asolvent or thinner can be supplied by gravity through a solvent conduit55 to the side outlet of the T-fitting 52 through any suitable flowcontrol valve 56.

It is desired to call attention to the fact that by substituting ahollow tube in the barrel 15 of Fig. 2 in place of the tubular heatingelement 20, the device may be used for chilling surface-coating-fluidsbefore entry into the gun. This is rarely required, but becomes veryimportant when spraying exceedingly low viscosity surface coatings, suchas zinc chromate compounds and the like. To spray the latter compoundsusually requires a reduction in the air trigger to preventoverapplication and running of the compound. By employing a cooling tubein place of the heater and connecting this tube with any suitablerefrigerant source, the fluid can be chilled as it passes through thebarrel 15 to a proper viscosity for application with a standard airpressure, thus avoiding all air pressure manipulation.

While a specific form of the improvement has been described andillustrated herein, it is desired to be understood that the same may bevaried, within the scopeof the appended claims, without departing fromthe spirit of the invention.

Having thus described the invention, what is claimed and desired securedby Letters Patent is:

1. A heating device for surface-coating spray guns comprising: acylindrical barrel; a vertical surface-coatingfluid chamber extendingthroughout the length of said barrel; means for connecting the upperextremity of said chamber to a spray gun; means'for supplyingsurfacecoating-fluid to the lower extremity of said chamber; anelectrical heating element positioned in said barrel exteriorly of saidchamber; and a tetracresylsilicate having a boiling temperature inexcess of 500 F. positioned in the space in said barrel about saidchamber.

2. A heating device for surface-coating spray guns comprising: acylindrical barrel; a vertical surface-coatingfluidchamber extendingthroughout the length of said barrel; means for connecting the upperextremity of said chamber to a spray gun; means for supplyingsurfacecoating-fluid to the lower extremity of said chamber; anelectrical heating element positioned in said barrel exteriorly of saidchamber; and a fluid having a boiling temperature in excess ofthat ofWater positioned in the space in said barrel about said chamber.

References Cited in the file of this patent UNITED STATES PATENTS351,014 Wissler Oct. 19, 1886 1,670,506 Johnson May 22, 1928 1,981,632Northrup Nov. 20, 1934 2,142,984 Thurman Jan. 3, 1939 2,307,924Gillespie Jan. 12, 1943 2,407,562 Lofgren Sept. 10, 1946 2,438,637Jansen Mar. 30, 1948 2,481,813 Bede "Sept-13, 1949 2,510,235 Kogel "June6, 1950 2,546,741 Grossman Mar. 27, 1951 FOREIGN PATENTS 608,376Great'Britain Sept. 14, 1948

